Method of and apparatus for utilizing the formation energy of petroleum deposits



, 1964 R. SCHIEL 3,161,593

METHOD 0 ND APPARATUS FOR LIZING THE FORMAT ENERGY PETROL DEPOSITS Filed March 29, 1960 3 Sheets-Sheet 1 Rik/MRO. sch/[EL INVENTOR.

Dec. 15, 1964 sc 3,161,593

METHOD AND APPA US FOR LIZING THE FORMA N ENERGY PETROL DEPOSITS Filed March 29, 1960 3 Sheets-Sheet 3 INVENTOR. FIG/6RD J (HIE L United States Patent 3 161,593 WTHGD tin ANS AiPARATUS FQR UTKLEZ'EZNG THE FU RMATlGN ENERGY 9F PETRGLEUM DEPUSTTS Richard Schiel, Stuttgart-Lederberg, Germany, assrgnor to Fa. Sehoeller-Bleeirman Stalilwerlre Alztiengesellschaft, Vienna, Austria Filed Mar. 29, 196i), tier. No. 18,293 Claims priority, application Germany, Apr. 2, 1959, Sch 25,815 8 Claims. (ill. 233-21) It is an object of the invention to provide a method, and an apparatus for carrying out this method, which enable the utilization of the formation energy to a much higher degree than is possible today. It is known that petroleum deposits contain a mixture of crude oil and of gas which is at least partly dissolved therein and of smaller amounts of salt water and impurities such as suspended clay and sand. This mixture is under a relatively high pressure in its deposit and has a temperature which is in most cases much higher than that at the surface. Whereas part of this formation energy is utilized to force the crude oil into the well and to raise it therein in the production of the crude oil, the surplus energy is then wasted to a large extent by throttling, pipe friction and the cooling of the crude oil. it is another object of the invention to decompose the crude oil to a larger extent into its components, namely, pure oil, gas, salt water and solids, simultaneously with the utilization of energy. This decomposing operation is also carried out today but requires sometimes the use of fairly expensive apparatus such as de-emulsifiers.

It is usual to incorporate nozzes in the eruption heads of flowing wells or of gas lift Wells, to expand the mixture of crude oil and. gas in these nozzles and then to feed it to a separator which separates the gas from the oil under a lower pressure and removes also part of the water and other impurities. These separators are in most cases upright or horizontal cylindrical pressure vessels, e.g., 1 meter in diameter and 6 meters long. These separators have various disadvantages, some of which will be outlined hereinafter:

The separator must be relatively large because Water and sand and other impurities will only separate from the oil when the same has been relatively stilled. The large volume renders the separator very expensive as it must be a pressure vessel.

For this reason it has repeatedly been attempted to effect a tangential introduction of the crude oil into the known separator in order to bring about a better purification by centrifugal force. Practice has shown, however, that such improvements are only insignificant. The tangentially admitted oil flows much too slowly to pro duce an appreciable effect. The friction on the separator Wall is so large that a high twisting speed involving an appropriate action of centrifugal force cannot be achieved.

It has also been attempted to purify the oil by centrifuges driven externally. This method can only be used, however, if the oil has already given off its gas in a separator before the centrifuge and the coarse mechanical impurities have also been removed because the known centrifuges do not afford space for a separation of gas. The high power required for driving from the outside renders the use of such centrifuges, in the number required to provide a centrifuge for each producing well, economically prohibitive.

If the oil is admitted tothe separator together with a large amount of gas, the complete separation of the drops of oil from the gas is difficult. For this purpose a fairly large number of parallel plates or perforated tubes must be incorporated in the known separator, whereby the proximately tangentially to a nozzle of a freely rotating weight and price thereof are increased. When the amount of gas is large, a perfectly pure, colorless gas cannot be obtained at all in a single separator and several separators must be connected in series.

The salt-waiter admixtures which are contained in the crude oil and are deleterious to the further processing thereof are not completely removed in the known separators. If they are highly heated, which is very expensive, entrained salt water will be removed from the oil as such and can be withdrawn from the bottom of the separator. The salt water which has already formed a fine emulsion with crude oil, however, is not separated. This emulsion remains in the crude oil and its decomposition requires an expensive aftertreatment of the oil.

Even the solid admixtures of the crude oil are only partly separated in the known separator owing to the short time available. Particularly the finer clay particles remain partly suspended in the oil and subsequently contaminate the oil tanks, pipelines etc.

Up to the present time the considerable pressure energy still contained in the oil-gas mixture in the eruption head is dissipated by expanding the mixture behind the eruption head without utilization of this energy. In producing Wells having a high pressure and a high gas-oil ratio this involves a considerable waste of energy. As the oil requires pressure to flow into the oil pipelines, this energy must be produced, which involves high operating costs and expenditures for pumps, electric energy or steam power.

In some cases so-called high-pressure separators have been connected before the usual separators. In these high-pressure separators part of the gas mixture is separated under a higher pressure, which is closer to that prevailing in the eruption head. Whereas this enables a saving of pressure energy of thergas, this separator has all the other disadvantages mentioned. The expenditure for these additional high-pressure separators is particularly high and in most cases is not economical. For this reason high-pressure separators are only rarely found in oil fields Whereas: most producing wells are provided with a low-pressure separator.

The high-pressure separator has basic disadvantages too. Whereas the separated high-pressure gas might be fed to a gas turbine this involves such a high investment and its operation becomes so complicated, owing to the fluctuations in the rate of gas production and of the pressure of the gas produced as Well as the considerable cooling during the expansion of gas, that it was not possible to use such special gas turbines. For this reason the pressure energy of the gas from the high-pressure separator can be utilized in practice only to feed the gas under the highest possible pressure to a directly subsequently connected compressor, which enables, e.g., the elimination of the first compressor stage. Such compressor stages, however, are only rarely available close to the bore holes. For practical reasons they can be exactly adjusted to the gas pressure of the respective well only in rare cases.

The main disadvantage of the high-pressure separators, however, resides in the fact that the high-pressure energy of the oil cannot be utilized. This energy is fairly considerable because the oil under pressure contains a large amount of gas in solution as well as the major part of the suspended solids. For this reason a subsequent hydraulic turbine would soon be made unusable by the erosion caused by the liquid droplets in the gas stream and the entrained sand.

The method and apparatus according to the invention I avoid these disadvantages.

In accordance therewith the mixture of crude oil,,gas, salt water and solids is fed as a foam from the inside apdrum, this nozzle having been specifically designed for a foam, and throttling of the mixture is avoided as far as possible. This drum rotates freely about a, say, vertical axis in a pressure-sealed vessel. Owing to the intimate contact of the expanding gas with the oil in the form of foam the latter expands almost isothermally, particularly because the oil foam under falling pressure releases constantly fresh gas previously dissolved. Adjacent to the nozzles the rotating drum is driven to act as a turbine. As the centrifugal force causes the components to stratify in the drum in dependence on the weight of said components, the drum will then act also as a direct centrifuge. During the subsequent withdrawal of the liquid components through nozzles, which utilize the dynamic pressure the drum acts as a pump. The formation energy is thus utilized to decompose the crude oil into its components and at the same time to discharge the liquid components from the apparatus under a pressure which is much higher than the inlet pressure because the energy of the approximately isothermally expanding gas is utilized for this purpose. This utilization is effected in a machine in which the same machine element, namely, a drum which rotates freely about its axis, is used as a power-producing turbine, as a separating centrifuge op erating at about 10,000 times the force of gravity, and as a feeding device in the form of a novel centrifugal pump.

The apparatus proposed has only a small volume because components of the crude oil are separated therein by centrifugal force at high speed rather than by stilling of the liquid. Owing to the high speed of its drum (e.g., 8000 revolutions per minute) the separation of the crudeoil component is effected instantaneously and fairly completely so that a large part of the emulsion of salt water and crude oil is also decomposed. In spite of the provision of the rotary drum the proposed centrifugal sepator is inexpensive because in machines produced in quantity the lower weight will result in lower manufacturing costs. The proposed centrifugal separator, however, replaces not only the usual separator but also the expansion nozzle of the eruption head. In this separator the original energy of the mixture of crude oil and gas is first converted into kinetic energy consisting of the angular velocity of the rotating drum. This is then utilized to separate the components of the crude oil by centrifugal force and to raise the separated pure oil and salt water to a high pressure, which is much higher than the initial pressure of the mixture. This is due to the fact that the gas is expanded during the separation and remains expanded. The energy released during the expansion of the gas may be transmitted to the oil to impart a very high velocity thereto, which can then be converted back into pressure. As a result, the pure oil can flow from the centrifugal separator directly to the pressure-oil pipelines and all investment for storing the oil in tanks, for pumps, for electric power or steam power become superfluous.

The accompanying diagrammatic drawing serves to explain the invention with reference to an embodiment and to enable an understanding of further details of the same.

In this drawing:

FIG. 1 is a partial longitudinal sectional view of the proposed centrifugal separator;

FIG. 2 is a cross-sectional view taken on line II-II of FIG. 8 shows on a larger scale a vertical joint of the drum wall;

FIG. 9 is a graph illustrating the theoretical heat balance;

FIG. 10 shows the pure-oil outlet pressures achievable with an assumed efiiciency based on experience; and

FIG. 11 is a longitudinal sectional view showing a vertical joint in the pure oil discharge conduit.

In a pressure-sealed housing, which consists of a bottom 1 with feet 2, a shell 3 and a cover 3a with a stuffing box 4, a stationary inlet pipe 5 terminates in an expansion nozzle 6, a stationary discharge pipe 7 which is screwed to the housing and terminates in a withdrawing nozzle 8. Nozzle 6 is in the form of a disk member, as best seen in FIG. 4, provided with a pair of generally radial passages 6', 6" whose terminal portions near the disk periphery are almost tangentially disposed. A self-supporting drum consisting of a base 9, a lower partition disk 10, an intermediate member 11, an upper partition disk 12 and a top 13 is mounted in bearings 14 and 15 on the inlet pipe 5. The lower bearing 14 is of the self-aligning type and carries the entire Weight of the drum. The upper bearing 15 is surrounded by a resilient part 16, e.g., a rubber ring. The drum accommodates also radial plates or vanes 17, 18, 19, 20, 21, 22 each of which is firmly connected e.g., by welding, to one of the parts 9-13 which are screwed together. An inclined additional discharge pipe 23, which is displaceable in its longitudinal direction, extends into the top 13 of the drum. A gas is discharged through the pipe 24. To measure the speed of the drum and for maintaining a predetermined speed of the drum by a motor or brake, if required, a gear wheel 25 is firmly connected to the drum and in mesh with a gear wheel 26 whose shaft 27 extends through a stufiing-box 2 8 out of the housing and has connected thereto, e.g., a motor or only a tachometer.

To effect a good seal between the several parts of the drum, a ring 29 or 29', e.g., of rubber, is inserted in each of the annular clearances at the end of the screw threads, as is shown in FIG. 8. This ring is urged by centrifugal force against the screwed joints and tightly seals the same. The crude oil enters the inlet pipe 5 under pressure Without having previously been expanded in the eruption head of the producing well. The crude oil consists of several components such as oil, gas, water, emulsion, clay particles, sand. The gas itself is partly dissolved in and partly mixed with the oil and together with the oil forms a dense foam. In the expansion nozzle 6 the mixture of crude oil and gas is accelerated in accordance with the known laws for the expansion in nozzles. A smaller part of the resulting kinetic energy at the nozzle outlet is due to the pressure drop of the oil component. A much greater part is delivered, however, in most cases by the gas which expands and dissolves. This gas undergoes an adiabatic expansion first, whereby it is cooled. Owing to the intimate contact of the gas bubbles with the oil and to the continual release of the gas particles from the oil as a result of the pressure drop, the cooling gas continuously absorbs heat from the oil. The specific heat of the oil is much larger than that of the gas. As a result the expansion of the entire foam is in fact not adiabatic but almost isothermal. This results in a higher kinetic energy and consequently in a higher discharge velocity than in a perfectly adiabatic process. The cross-section of the expansion nozzle 6 must be appropriate for this kind of expansion. For this reason the gas must expand even more than is usual in conventional Laval nozzles. (This is not apparent in the drawing owing to the small scale.) By virtue of the aforedescribed shape of the passages 6', 6 of the expansion nozzle 6 the flowing mixture, which is first radially outwardly directed, is increasingly deflected into the tangential direction so that the mixture is finally admitted to the drum tangentially from the inside and impinges on the angularly spaced vanes 19 (see FIG. 4) almost at right angles to their radial flanks. As a result the freely rotatable drum is driven and is accelerated until its peripheral velocity approximates the velocity at which the mixture is discharged from the expansion nozzle 6. This velocity may be, e.g., 150 meters per sec ond. The centrifugal force causes the liquid to form a peripheral layer on the inside wall of the drum. On ac count of the centrifugal force, which is about 10,000 times the force of gravity, their components separate immedi ately in accordance with their specific gravity. Thereby the gas bubbles are squeezed out inwardly and the water together with the solids (sand, clay) moves to the outer boundary. The next inner layers consist of the emulsion and the oil, in this order. The emulsion of salt water and oil is finally decomposed into its components. This will take place particularly quickly if emulsion-breaking chemicals have previously been added to the crude oil. The gas is discharged from the open-topped and open-bottomed drum into the housing and into the gas outlet pipe 24 under a pressure of, e.g., 7 kg./sq. cm. superatmospheric pressure. If the pressure of the inllowing mixture was, e.g., 27 kg./sq. cm. superatmospheric pressure, this means that the expansion of the gas has caused a pressure drop of 20 kg./sq. cm. and a delivery of the corresponding amount of energy to the rotating drum. The oil with the water and solids flows towards the top, where the oil enters the tangential withdrawing nozzle 8 at a high speed (e.g., of 150 meters per second) and is continuously decelerated there and at the same time is deflected into the radial direction. It is thus caused to flow into the discharge pipe '7 under high pressure, e.g., of 110 kg./sq. cm. superatmospheric pressure, and to leave the separator. Even in the case of considerable losses by liquid friction this outlet pressure of the oil is considerably higher than the pressure with which the mixture enters the separator. The differential energy is delivered by the expanding gas. Being heavier than oil, the water with sand and clay enters the upper space of the top 13, owing to the approximately frusto-conical shape of the drum, where this water is withdrawn continuously or from time to time under pressure by the discharge pipe 23 pushed into the water. This circulating pipe acts also as awithdrawing nozzle. The parts of the shell are screwed together with the aid of right-hand or left-hand screw threads selected to cause a tightening of the threads dur ing starting up and during operation. In order to provide for a predetermined oil-outlet pressure (p2) in the case of a given pressure (p1) of the mixture, it is desirable to insert a control valve 40 in the gas line 24 behind the separator. The more this valve is opened the smaller will be the gas pressure in the housing and the greater will be the rise in the oil outlet pressure p2.

To simplify the assembly and to reduce the manufacturing costs it is advantageous not to make the various parts of the apparatus, such as the parts 7, S, 5 and d, in one piece, as is shown in FIG. 1 for the sake of clarity, but to make them in the form of separate parts, which are subsequently screwed together.

Tests have shown that it is diflicult to provide a screwed joint which is sufficiently reliable in operation. Thus, if parts 6 and 5 are screwed together in such a manner that the screwed joint is tightened when the parts are driven, the frictional drag will tend to loosen it during idling. For this reason such parts are connected according to the invention by a double screw thread, which has given best results in operation. If it is desired, e.g., according to FIG. 11, to connect two pipes 33 and 34, a cap nut 35 is also used for this purpose as well as collars 36 and 37 forced against each other. The pipes 33 and 34 are screwed together by means of, say, a left-hand screw thread in such a manner that the collars 36 and 37 are in firm and tight engagement. Then the cap nut 35 is screwed to the collar 37 with an oppositely handed, in this case a right-hand screw thread, to force the collar 36 also against the collar 37. If the pipe 33 tends to turn left relatively to the pipe 34, this will be prevented by the lefthand screw thread 38, which will be tightened even more. If the pipe tends to turn right, this will be prevented by the right-hand screw thread 39. As a result such a connection will resist any rotation in either direction and is perfectly tight whereas it can easily be taken apart by loosening the cap nut 35. The upper bearing 15 being resiliently supported on the outside, the inevitable rotary unbalance of the drum can adjust itself to its free axis. As a result, not only does the drum rotate calmly but the bearing 15 will not wobble because it will always rotate centrically and a displacement will take place only in the resilient part 16 and only during starting. This is in contrast with known resilient bearings of centrifuges in which the shaft is rotated too and the bearing is resiliently cushioned on the outside. Whereas this eliminates the rotary unbalance of the centrifuge, it will not eliminate the wobbling of the corresponding bearing itself.

In addition to the bearing friction the separator according to the invention has no sliding parts. For this reason it does not need special attention once it has been started and if made of corrosion-resisting material has a practically unlimited life. Parts 25 to 28 of FIG. 1 may be omitted if the speed is determined by vibration meters, for example. Owing to the rapid separation of the components of the crude-oil mixture by the great centrifugal force the separator according to the invention may be of very small size. For a producing well it may have an overall diameter of about 0.5 meter and an overall height of 0.6 meter. As contrasted therewith the usual separators are about 1 meter in diameter and 6 meters in height. It will be appreciated that the proposed separator is highly superior to the usual ones not only in its effect but also in its manufacturing cost. Owing to the automatic balancing by the resilient bearing it requires no parts which must be finely machined, with the exception of the nozzles.

In FIG. 9, the left-hand column shows by way of example the energy contained in one cubic meter of crudeoil mixture at a pressure of 27 kg./ sq. cm. superatmospheric pressure and a gas-oil ratio of 80. This is the state before the usual nozzle in the eruption head. It will be apparent that the part of the energy contained in the gas 31 greatly exceeds that in the oil 30. The right-hand column indicates the amount of energy still contained in a mixture of crude oil and gas in a separator under a pressure of 7 lag/sq. cm. superatmospheric pressure. This is the state of the mixture in one of the usual separators. The difference 32 between the heights of the left and right columns was previously wasted in the nozzle of the eruption head by turbulence without utilization. In accordance with the invention this differential energy is utilized to impart a pressure which is higher than the inlet pressure to the oil which has been separated from the mixture.

It is apparent from the diagram of FIG. 10 that the oil outlet pressure p2 will be the higher the lower is the separator outlet pressure p3 of the gases for a given initial pressure pl. In practice the gas outlet pressure )3 will not be lower than required to provide reliably for the oil outlet pressure p2 required by the oil pipelines because it is desirable to discharge also the gas at the highest possible pressure in order to impart a high, power-saving intake pressure at any existing compressors connected to the gas pipelines. In this way the object set forth is accomplished, i.e. the crude-oil mixture is decomposed into its components by a relatively small apparatus and is separated from them and leaves the separator at a pressure sufficient to enable it to fiow directly to the crude-oil pressure pipelines without need for additional pumps.

It may be advantageous to heat the crude oil mixture somewhat before it enters the separator in order to avoid any separation of paraflin in the drum which might otherwise occur.

If particularly high peripheral speeds are to be reached in the drum it is convenient to make the base 9, the partitions 10 and 12 and the top 13 thicker on the inside than on the outside so that disks of approximately equal strength are obtained which will support the drum disks.

The most favorable location of the apparatus described is the lower end of the tubing, i.e. inside the casing above a packer. Owing to the better accessibility a location on the surface close to the producing well may also be selected. In special cases it may be desirable to connect two of said apparatus in series, e.g., for treating an emulsion. In that case the first apparatus separates the pure oil from the gas and the impurities and the second separates the salt water from the emulsion. The latter may then be fed back to the cycle, e.g., after an addition of chemicals.

I claim:

1. A method of separating, with the aid of a rotatable centrifuge drum, oil from contaminants having a higher specific gravity than said oil in a crude petroleum foam issuing from a petroleum deposit and charged with a gas under pressure, comprising the steps of introducing said foam into said drum; rotating said drum by substantially isothermally expanding said gas to produce a high-velocity jet of said foam and directing said jet generally tangentially into said drum to drive it with a velocity sufficient to concentrate said contaminants at an outer zone, said oil in a layer along an inner wall of said drum at an intermediate zone and said gas at an inner zone thereof; discharging said contaminants from said outer zone and said gas from said inner zone; imparting an angular velocity to said oil by entraining it along with the rotating drum; and withdrawing said oil from said drum under pressure substantially tangentially at a location in said intermediate zone by intercepting said layer along said wall with an outlet body projecting generally radially into said layer.

2. An apparatus for separating a liquid from contaminants having a specific gravity higher than that of said liquid and a gas in a lfluid mixture under pressure, comprising a pressure chamber,'a drum resiliently journale for rotation in said chamber about a substantially vertical axis, said drum having an upwardly diverging conical interior wall, conduit means for said fluid leading axially into said drum, stationary nozzle means supplied by said conduit means for expanding said mixture and directing it substantially tangentially against said wall, thereby rotating said drum and centrifugally separating said liquid and said contaminants from said gas, vane means within said drum for rotatingly entraining said liquid and said contaminants separated from said gas to produce a layer of said liquid lying along said wall, first discharge means relatively close to the said axis leading from said drum for removing said gas therefrom, second discharge means, including a stationary body projecting into said layer and provided with a mouth intercepting said layer, spaced above said nozzle means and relatively remote from said axis for removing said liquid from said drum substantially tangentially, and third discharge means outwardly from said second discharge means for removing said contaminant.

3. An apparatus according to claim 2, further comprising at least one peripherally perforated disc secured to said drum and extending transversely to said axis between said nozzle means and said second discharge means.

4. An apparatus according to claim 2 wherein said second discharge means includes a pipe leading axially away from said drum and a conduit member having a bore opening at said mouth in the path of the liquid entrained by said vane means, said bore terminating at said pipe and gradually increasing in its cross-sectional area in the direction thereof.

5. An apparatus according to claim 2 wherein said vane means includes a plurality of blades co-operating with said second discharge means for urging said liquid out of said drum.

6. An apparatus according to claim 4 wherein said nozzle means comprises a disk member extending generally transversely to said axis within said drum and defining with said wall a limited peripheral clearance, said disk member being provided with a generally radial passage communicating with said conduit means and terminating at the periphery of said disk member in a portion extending generally tangentially thereto for directing a substantially tangential jet of said mixture against said wall while permitting substantially isothermic expansion of said gas.

7. An apparatus for separating a liquid from contaminant-s having a specific gravity higher than that of said liquid and a gas in a fluid mixture under pressure, comprising a housing forming a pressure chamber; a centrifuge drum resiliently journaled in said housing for rotation within said chamber about a substantially vertical axis, said drum having an upwardly diverging conical interior wall centered on said axis; conduit means for said mixture leading axially into said drum; a stationary nozzle within said drum supplied by said conduit means comprising a disk extending generally transversely to Said axis within said drum and forming with said wall a limited peripheral clearance, said disk being formed with at least one generally radially extending bore communicating with said conduit means and terminating at the periphery of said disk in a passage for directing a generally tangential jet of said mixture against said wall, said drum being formed in the region of said disk with a plurality of angularly spaced vanes extending from said wall into said clearance whereby said drum is rotated by said jet; vane means within said drum for rotatably entraining therewith a layer of said liquid centrifugally held along said wall; first discharge means relatively close to said axis leading from said drum for removing gas separated from said mixture away from said chamber; second discharge means including a stationary body extending generally radially from said axis toward said wall into said layer, said body having a mouth in intercepting relationship with said layer for removing said liquid from said drum and a generally radially extending bore communicating with said mouth, and other conduit means communicating with the bore in said body for conducting said liquid away from said chamber, said body being disposed axially above said disk; and third discharge means for removing the contaminants centrifugally separated from said liquid.

8. An apparatus for separating a liquid from contaminants having a specific gravity higher than that of said liquid and a gas in a fluid mixture under pressure, comprising a housing forming a pressure chamber; a centrifuge drum resiliently journaled in said housing for rotation within said chamber about a substantially vertical axis, said drum having an upwardly diverging conical interior wall centered on said axis; conduit means for said mixture leading axially into said drum; a stationary nozzle within said drum supplied by said conduit means comprising a disk extending generally transversely to said axis within said drum and forming with said wall a limited peripheral clearance, said disk being formed with at least one generally radially extending bore communicating with said conduit means and terminating at the periphery of said disk in a passage 'for directing a generally tangential jet of said mixture against said wall, said drum being formed in the region of said disk with a plurality of angularly spaced vanes extending from said wall into said clearance whereby said drum is rotated by said jet; vane means Within said drum for rotatably entraining therewith a layer of said liquid centrifugally held along said wall; first discharge means relatively close to said axis leading from said drum for removing gas separated from said mixture away from said chamber; second discharge means including a stationary body extending generally radially from said axis toward said wall into said layer, said body having a mouth in intercepting relationship with said layer for removing said liquid from said drum and a generally radially extending bore communicating with said mouth, and other conduit means communicating with the bore in said body for conducting said liquid away from said chamber, said body being disposed axially above said disk; third discharge means for removing the contaminants centrifugally separated from said liquid; and control means for adjustably throttling the efllux of said gas from said 5/10 Richardson 233-49 11/40 Stigen 233 22 Smith 55-203 X Cresswell 233-22 Kusserow et a1. 55-203 X Caddell 233-24 X Cornell 23321 X HARRY B. THORNTON, Primary Examiner.

HERBERT L. MARTIN, WESLEY S. COLE, Examiners, 

1. A METHOD OF SEPARATING, WITH THE AID OF A ROTATABLE CENTRIFUGE DRUM, OIL FROM CONTAMINANTS HAVING A HIGHER SPECIFIC GRAVITY THAN SAID OIL IN A CRUDE PETROLEUM FOAM ISSUING FROM A PETROLEUM DEPOSIT AND CHARGED WITH A GAS UNDER PRESSURE, COMPRISING THE STEPS OF INTRODUCING SAID FOAM INTO SAID DRUM; ROTATING SAID DRUM BY SUBSTANTIALLY ISOTHERMALLY EXPANDING SAID GAS TO PRODUCE A HIGH-VELOCITY JET OF SAID FOAM AND DIRECTING SAID JET GENERALLY TANGENTIALLY INTO SAID DRUM TO DRIVE IT WITH A VELOCITY SUFFICIENT TO CONCENTRATE SAID CONTAMINANTS AT AN OUTER ZONE, SAID OIL IN A LAYER ALONG AN INNER WALL OF SAID DRUM AT AN INTERMEDIATE ZONE AND SAID GAS AT AN INNER ZONE THEREOF; DISCHARGING SAID CONTAMINANTS FROM SAID OUTER ZONE AND SAID GAS FROM SAID INNER ZONE; IMPARTING AN ANGULAR VELOCITY TO SAID OIL BY ENTRAINING IT ALONG WITH THE ROTATING DRUM; AND WITHDRAWING SAID OIL FROM SAID DRUM UNDER PRESSURE SUBSTANTIALLY TANGENTIALLY AT A LOCATION IN SAID INTERMEDIATE ZONE BY INTERCEPTING SAID LAYER ALONG SAID WALL WITH AN OUTLET BODY PROJECTING GENERALLY RADIALLY INTO SAID LAYER. 